The application of conversion coatings on zinc surfaces prior to the application of a siccative film is well known in the industry. It is also known that a conversion coating can be applied to zinc surfaces from an alkaline solution due to the amphoteric properties of zinc metal.
U.S. Pat. No. 3,444,007, issued May 13, 1969 to James I Maurer et al. describes a process for applying a conversion coating to zinc surfaces using an alkaline solution of a metal ion other than an alkali metal ion, and a complexing agent to hold the metal ion in solution.